This invention relates to an induction system for an internal combustion engine and more particularly to an improved induction system that permits better exhaust emission control while, at the same time, affording good fuel economy. In addition, the invention relates to an improved injection system for a multiple intake passage system for an engine.
It is well known that a variety of arrangements have been incorporated for improving exhaust gas emission control and particularly for controlling the emission of hydrocarbons, carbon monoxide and NOx in the exhaust gases of an engine. Unfortunately, many of the aspects employed to provide exhaust emission control can deteriorate the fuel economy of an engine.
In addition to exhaust emission control and fuel economy, it is also desirable to provide good running characteristics for the engine through its entire speed and load range. One way in which these varying conditions can be met is through the use of a compound induction system for the engine wherein low and mid-range performance is supplied by a single, relatively small intake passage to offer good turbulence in the combustion chamber while high speed requirements are provided by a larger effective passage so as to improve volumetric efficiency. Normally this type of compound induction system incorporates at least two intake passages that serve each combustion chamber with a throttle valve arrangement for controlling the flow through one of the intake passages so that it will supply no charge under low and mid-range load conditions. However, the existence of this additional passage and its flow control valve can give rise to pumping losses that deteriorate the fuel economy of the engine when the control valve is closed.
It is, therefore, a principal object of this invention to provide an improved induction system for an engine wherein good performance results under all running conditions and at the same time effective exhaust emission control is achieved.
It is a further object of this invention to provide an improved induction system for an engine that permits the aforenoted results while, at the same time, eliminating or substantially reducing pumping losses under low and mid-range performance so as to improve fuel economy.
One way in which NOx emissions are controlled is through the use of exhaust gas recirculation (EGR). Recirculating exhaust gases into the combustion chamber under at lease some running conditions reduces the temperature in the combustion chamber and the formation of NOx. However, the use of EGR can give rise to poor running characteristics when large quantities of exhaust gases are recirculated. In addition, many engines are very sensitive to the amount of the EGR.
It is, therefore, a still further object of this invention to provide an improved system for permitting increased usage of EGR without deteriorating engine performance.
It is a further object of this invention to provide an EGR system for an engine having a compound induction system wherein the EGR is employed to reduce pumping losses as well as controlling the emission of NOx.
With compound induction systems, it is frequently the practice to inject fuel in such a manner that a single fuel injector can supply fuel to all induction passages serving a given combustion chamber. However, when there is no flow occurring through certain of the induction passages under some running conditions, any fuel injected into this passage will be lost or can cause other disadvantageous results. Therefore, it is frequently proposed to employ multiple fuel injectors in such systems, which expedient adds to the cost and complexity of the system.
It is, therefore, a still further object of this invention to provide an improved fuel injection system for a compound induction system wherein only a single fuel injector is employed and means are provided for selectively controlling the spray pattern of the fuel injector.